<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        //赋值运算符 =
        var num1 = 100;
        var num2 = num1;
        console.log(num2);

        // += x+=y => x=x+y
        var x = 10;
        var y = 10;
        // console.log(x += y);
        console.log(x -= y);



    </script>
</body>
</html>